International publication number WO 01/02092 (Akzo) discloses a process for regenerating a used additive-based catalyst by contacting it with an oxygen-containing gas. The regenerated catalyst is rejuvenated by contacting it with an organic additive followed by drying to remove the additive solvent therefrom. The publication discloses that the regenerated and rejuvenated catalyst may also be presulfided, but it fails to in anyway describe the presulfiding methodology, and it fails to teach presulfurization using elemental sulfur. The publication further fails to teach revitalization of a catalyst using a chelation mechanism, and it especially fails to teach the use of a chelant in combination with aging to provide for a revitalized catalyst. It is especially noteworthy that the teachings of the publication only relate to an additive-based catalyst. The publication does not provide any teaching regarding the calcination of the regenerated catalyst that has had incorporated therein the organic additive.
U.S. Pat. No. 6,239,054 B1 discloses the use of a chelating agent in a process for improving the activity of a spent catalyst by treating the spent catalyst with a chelating agent followed by drying and calcining. The claimed process requires the calcining step. There is an ongoing need to find better methods for restoring the activity of catalysts that have lost activity due to their use, particularly, when the catalyst is a spent high activity hydrotreating catalyst.